Rapid and sensitive XAFS using a tunable X-ray undulator

SUMS: synchronous undulator-monochromator scans at Synchrotron Soleil

A strategy for performing synchronous undulator-monochromator scans (SUMS) compatible with the control system of Synchrotron Soleil has been developed. The implementation of the acquisition scheme has required the development of an electronic interface between the undulator and the beamline. The characterization of delays and jitters in the synchronous movement of various motor axes has motivated the development of a new electronic synchronization scheme among various axes, including the case when one of the axes is electronically accessible in `read-only' mode. A software prototype has been developed to allow the existing hard continuous software to work in user units. The complete strategy has been implemented and successfully tested at the TEMPO beamline.

Size-selective extended X-ray absorption fine structure spectroscopy of free selenium clusters

In a recent paper [M. Yao et al., J. Synchrotron Radiat. 8, 542 (2001)]], we proposed a new method for the size-selective EXAFS (extended x-ray absorption fine structure) of neutral-free clusters, in which not only the x-ray absorption process but also the deexcitation processes are utilized as the structural information. In order to verify this method experimentally, we have developed the synchronous measurements of EXAFS and photoelectron photoion coincidence and carried them out for a Se cluster beam by utilizing the third-generation intense x-ray source. The EXAFS spectra for Se small clusters have been obtained and compared critically with theoretical predictions.